Poppets are valve members and are commonly used for closing or seating on valve seat on a valve opening to prevent or to permit fluid flow through the valve opening.
Typically, the poppet has a cylindrically shaped stem disposed along a longitudinal axis and a larger diameter cylindrically shaped valve head. The valve head has a sealing surface such as a tapered edge which is adapted to sealingly engage a seating surface such as a tapered surface about a valve opening. In certain applications, a poppet is closed or moved to a closed condition by an independent spring member acting in one longitudinal direction on the body of the poppet and is opened or moved to an opened condition by a force such as an independent actuating member or fluid pressure acting in an opposite longitudinal direction on the poppet.
Where precise seating of a valve head with a seating surface about a valve opening is required, the stem is machined to a tight (small) tolerance with respect to a stem guide bore to maintain alignment of the sealing surfaces on the valve head and the valve opening while the poppet is slidably moved between an open and a closed condition. In certain instances, the fluids passing through the valve will contain contaminants or components which can build up as a residue on the sliding surfaces between the stem and the guide bore. Such residue can and does prevent the poppet from properly sealing. If the poppet fails to operate properly, in space operations for example, couplings can not be disconnected safely.
Where the poppet stem has a sliding surface in a bore, wear of the surfaces also occurs which can lead to contamination build-up and/or loose fits which affect the operation of the poppet.